It is well established that the bone mineral density. of males decrease with age. Decreased amounts of bone mineral content and density correlate with decreased bone strength and predispose to fracture. The molecular mechanisms underlying the pleiotropic effects of sex hormones in non-reproductive tissues are only beginning to be understood, but it is clear that physiologic concentrations of androgens and estrogens play an important role in maintaining bone homeostasis throughout the life cycle. Consequently, when androgen or estrogen deprivation occurs, there is a resultant increase in the rate of bone remodeling that tilts the balance of resorption and formation in the favor of resorption, contributing to an overall loss of bone mass. In males, the natural decline in sex hormones at maturity (direct decline in androgens as well as lower levels of estrogens derived from peripheral aromatization of androgens) is associated with the frailty of bones. This effect is also observed in males who have been castrated.
Prostate cancer is one of the most frequently diagnosed noncutaneous cancers among men in the United States. One of the approaches to the treatment of prostate cancer is by androgen deprivation. The male sex hormone, testosterone, stimulates the growth of cancerous pro static cells and, therefore, is the primary fuel for the growth of prostate cancer. The goal of androgen deprivation is to decrease the stimulation by testosterone of the cancerous prostatic cells. Testosterone normally is produced by the testes in response to stimulation from a hormonal signal called luteinizing hormone (LH), which in turn is stimulated by luteinizing-hormone releasing hormone (LH-RH). Androgen deprivation is accomplished either surgically by bilateral orchidectomy or chemically by LH-RH agonists (LHRH) with or without nonsteroidal antiandrogens.
Current studies suggest that early androgen deprivation in patients with micrometastatic disease may indeed prolong survival [Messing E M, et al (1999), N Engl J Med 34, 1781-1788; Newling (2001), Urology 58(Suppl 2A), 50-55]. Moreover, androgen deprivation is being employed in numerous new clinical settings, including neoadjuvant therapy prior to radical prostatectomy, long-term adjuvant therapy for patients at high risk for recurrence following radiation or surgery, neoadjuvant therapy for radiation, and treatment of biochemical recurrence following radiation or surgery [Carroll, et al (2001), Urology 58, 1-4; Horwitz E M, et al (2001), Int J Radiat Oncol Biol Phy Mar 15;49(4), 947-56]. Thus, more prostate cancer patients have become candidates for and are being treated by androgen ablation. Moreover, these prostate cancer patients are being treated earlier and longer than in the past, which in some cases may be as long as 10 or more years of androgen deprivation therapy.
Unfortunately, androgen deprivation therapy is fraught with significant side effects, including hot flashes, gynecomastia, osteoporosis, decreased lean muscle mass, depression and other mood changes, loss of libido, and erectile dysfunction [Stege R (2000), Prostate Suppl 10,38-42]. Consequently, complications of androgen blockade now contribute significantly to the morbidity, and in some cases the mortality, of men suffering from prostate cancer.
Given that more patients today are being treated by long-term androgen deprivation, osteoporosis has become a clinically important side effect in men suffering from prostate cancer undergoing androgen deprivation. Loss of bone mineral density (BMD) occurs in the majority of patients being treated by androgen deprivation by 6 months. New innovative approaches are urgently needed at both the basic science and clinical levels to decrease the incidence of androgen-deprivation induced osteoporosis in men suffering from prostate cancer.